Gadget Freak Case #230: The Inexpensive Dimmable LED Desk Lamp

With the cost of high-brightness LEDs coming down, Andrew Morris decided he wanted a dimmable LED desk lamp. Yet he found the ones on the market were very expensive, and few of them were dimmable. So he decided to use his engineering skills to build his own.

He installed his circuit into a fluorescent desk lamp he had picked up years ago at a flea market. He also discovered the LED driver circuit was dirt cheap and simple to assemble.

Andrew Morris designed a dimmable LED driver circuit that is simple and energy efficient. He then installedthe circuit into a portable fluorescent lamp.

I have a friend who is a member of a model railroading club. He wants to replace hundreds of small energy-hogging incandescent bulbs with LEDs. He is currently using triac-based dimmers. As long as he uses an isolation transformer or completely insulates all wiring, my circuit will be a safe and simple solution to his problem. I'm going to help him with that.

The lamp is identical to the one I demonstrated in the video, except that it is black. This lamp body is ideal for the LED conversion and it costs under $15 plus shipping. I like its compact footprint and the fact that it can be folded or rotated to shine light in any direction. I bought the last one they have in stock, but Amazon says that more are on the way.

The isolation transformer is not actually part of the project. It is a safety device for people who breadboard and test line-powered circuits that are not isolated from the power line. You should have an isolation transformer already if you do this kind of work. The components that are part of the lamp itself are quite cheap. If you just build the circuit and don't breadboard it or test it with anything but a voltmeter, you won't need an isolation transformer.

Nice application, Andrew. Looks like the only significant cost here was the isolation transformer, at $21. By the way, if you or any reader has a good LED holiday light application, please send me a photo. As we did last year, we'll be running good photos of LED light strings at the holidays. Send to charles.murray@ubm.com.

Thanks for the kind words. I'm a retired electrical engineer, living alone with nothing else to do. I don't sit around looking for stuff to create. It just happens. I see a want or need and create a solution. This blog needs more gadget submissions from other people. My ugly face is showing up a bit too often. :-)

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